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Hamstring Injuries

March 2012

Featured Story

Contributed by Derek Purcell, M.D.
As spring draws near, the occurrence of hamstring injuries will likely increase. Hamstring injuries are the most common muscle strains. The hamstring muscles are unique as they anatomically span two joints, the hip and the knee. Most strains are to the muscle belly at the musculotendinous junction and occur during an eccentric contraction when the hip is flexed and the knee is extended. Multiple factors have been associated with increased risk of hamstring injury: inflexibility, fatigue, poor technique, inadequate warm-up, strength imbalance, poor posture and leg length inequality. The vast majority of hamstring injuries may be treated in a conservative fashion, with the goals of starting early motion with formal physical therapy to promote muscle healing and avoiding scar formation. However, one must be aware of the possibility of proximal hamstring avulsion from the ischium. The mechanism of injury is the same but surgical intervention may indeed be required.

The presentation is often very similar to the more common musculotendionus injury. Patients present with a hip flexion knee extension avoidance gait and with pain when sitting, due to avulsion from the ischium. Most patients have extensive ecchymosis that extends down the posterior thigh to the knee. However, the appearance of this bruising is usually several days after the initial injury. A palpable defect may not be readily apparent, and care should be taken to carefully evaluate both the sciatic and peroneal nerve distributions. Injury may present as simply weakness of ankle eversion or frank foot drop.

Imaging with simple radiographs of the pelvis is necessary, as well as an MRI. Plain radiographs may reveal osseous avulsion of the hamstring origin from the ischium, though this is rare. An MRI is necessary to evaluate the extent of injury and is critical for determination regarding surgical indications. Single tendon avulsions of 1-2 cm should be treated non-operatively as the disrupted tendon will simply adhere to the remaining tendons. Injuries to two tendons that retract greater than 2 cm should be surgically repaired. Avulsions involving all three tendons should be repaired surgically. Ideally these injuries should be repaired acutely as delayed repair has less reliable outcomes.

The consequences of failure to recognize these injuries can be problematic. Patients will have residual hamstring weakness, sitting pain and the possible development of hamstring syndrome. Hamstring syndrome is related to the adherence of the sciatic nerve to the avulsed hamstring tendons resulting in chronic posterior thigh pain, weakness and difficulty sitting.

As with any lower extremity injury, care should be taken to be aware of the risk of lower extremity Deep Vein Thrombosis (DVT). Patients should be alerted to the signs and symptoms of DVT and the need for immediate evaluation if symptoms develop.